[updated with *] P85D 691HP should have an asterisk * next to it.. "Up to 691HP"

[stopcrazypp]

The car needs to sustain 691 HP for a period of time to be useful. If it can only output that much power for a few milliseconds, it is not of much use. If it does sustain 691 HP, then the averaged/smoothed power should reflect that.

No ICE sustains peak hp for a more than short while. Once you reach past a certain rpm point, you leave the peak power point (which is a single point at a certain rpm). Tesla's previous graphs did have a wide rpm range at peak power (and some diesels are like that too), but it's not typical. And Tesla doesn't have another gear to shift to either, so as it reaches higher rpms and the torque drops, you necessarily have to leave the peak power point.

 

[lphe]

I can record the electrical power input to the inverter/motor and the mechanical output power of the motor on my PHEV. When I plot either mechanical motor output power or electrical power input to the motor vs. speed during acceleration I observe a curve similar to the one plotted in post 256. Power peaks at around 30 mph and then flattens out. There are no abrupt changes in the curves. Of course, the PHEV motor outputs a lot less power than the Tesla's. I can measure the actual efficiency of the inverter/motor to be 86%.

 

[sorka]

The car needs to sustain 691 HP for a period of time to be useful. If it can only output that much power for a few milliseconds, it is not of much use. If it does sustain 691 HP, then the averaged/smoothed power should reflect that.

I'm unsure of the accuracy of the results plotted above. For one thing, they only reflect acceleration of the car. Additional power is required to overcome aerodynamic drag, internal friction, and tire rolling resistance. This power increases with speed. It might be around 15 kW for 60 mph. So the curve probably really flattens out at about 385 kW after 20 m/s.

All ICE motors only produce their peak power at exactly one RPM value in one instant.

The difference is that gears allow the engine to hover just before and after that for how ever many gears there are.

But the power curve on electric motors is so wide and flat you don't really need gears. You get 100% of torque at 0 RPMs.

 

[Danal]

I'm unsure of the accuracy of the results plotted above. For one thing, they only reflect acceleration of the car. Additional power is required to overcome aerodynamic drag, internal friction, and tire rolling resistance. This power increases with speed. It might be around 15 kW for 60 mph. So the curve probably really flattens out at about 385 kW after 20 m/s.

Backwards.

Delta speed / Delta time = Force used to move the car. Force over time = Power. All from measured data.

Any additional power absorbed into Aero, rolling, etc. must be produced by the motor IN ADDITION to the power that accelerates the car's mass. Phrased another way: If there is 15kW going into those other places, then the power produced by the motor would be EVEN MORE than the measurements & calculations indicate. .

 

[lphe]

See the following post for power and speed vs. time for an S 85. Power increases linearly until 300 kW and then flattens out.

Beta of a Hosted Data Logger via the Tesla API - Page 3

- - - Updated - - -

The rated power of the S 85 motor is 380 hp or 280 kW. The battery is outputting 300 kW. So the battery is capable of providing adequate power to the motor on the S85.

- - - Updated - - -

Backwards.

Delta speed / Delta time = Force used to move the car. Force over time = Power. All from measured data.

See the following link:

Power (physics) - Wikipedia, the free encyclopedia

 

[jdbob]

I have a PHEV. According to its specifications, the peak motor output is 88 kW. The peak battery output is, however 68 kW. So, as with the Tesla, the maximum power output of the motor is limited by the peak output power of the battery.

Tesla should state the maximum power output of the battery.

Sounds like a Ford Energi model. They used to just advertise the peak motor output (as 118hp) but eventually they started to put the actual power ratings on their website and brochure (68kW Charge Depleting and 35kW Charge Sustain).

They are importing some C-Max Energi's into the Netherlands but the brochure there only mentions the 88kW. I guess they do whatever they think they can get away with.

 

[Danal]

See the following link:

Power (physics) - Wikipedia, the free encyclopedia

First few sentences from your link:

In physics, power is the rate of doing work. It is equivalent to an amount of energy consumed per unit time. In the SI system, the unit of power is the joule per second (J/s), known as the watt in honor of James Watt, the eighteenth-century developer of the steam engine.

You are pedantically correct that I used the wrong word ("force") in my summary. The spreadsheet is correct. It calculates DV, DT, Newtons for 1kg, Newtons for the car, Newton/M/S. Please note that one Newton/M/S is one Watt. They are the SI standard of power. That is, one Joule per second, one Newton Meter Per Second, and one Watt are all the same thing. And that is exactly what the spreadsheet calculates before converting to HP.


Now that we've cleared that up, please address your statement:

Additional power is required to overcome aerodynamic drag, internal friction, and tire rolling resistance. This power increases with speed. It might be around 15 kW for 60 mph. So the curve probably really flattens out at about 385 kW after 20 m/s.

I believe the point you are making is backwards. Per the part of my quote you cut:

Any additional power absorbed into Aero, rolling, etc. must be produced by the motor IN ADDITION to the power that accelerates the car's mass. Phrased another way: If there is 15kW going into those other places, then the power produced by the motor would be EVEN MORE than the measurements & calculations indicate. .

Perhaps I'm just taking your wording backwards? Calculating the movement of the car, and the power required... the motor actually has to produce more power than that, to both overcome the drag and to move the car... yes? no?

 

[krisg81]

Although I'm impressed with the mathematicians in here and I like some of the info you guys are coming up with, let's consider the following.

1) Tesla advertises the P85D as 691HP. The S85 is advertised at 380HP, and the S60 is also advertised at 380HP.

2) There is little to no difference after 50MPH in acceleration across the P85D/S80/S60 fleet. Therefore advertised 691HP on the premium performance model is non-existent vs other models in the fleet. MORAL OF STORY: ADVERTISED 691 HORSEPOWER OF P85D IS ONLY TEMPORAILY AVAILABLE AT LOWER SPEEDS. In an ICE car, advertised HP is available AT ALL SPEEDS, but dependent on RPM - but you have all HP on tap at any speed (dependent on correct gear)

3) When fuel tank is low (battery) on P85D, performance suffers versus full tank (full charge). ICE vehicles don't care about the current level of fuel in the tank.

4) Since EV's peak horsepower seems to only work in a burst mode/temporary spike at low RPMs, why is Tesla able to advertise 691HP in the way a standard auto manufacturer rates an ICE vehicle? If a Corvette only outputted it's maximum advertised HP from 0-30MPH, and after that the same as a Camaro V6 with half the advertised power, the shat would hit the fan! There is a huge issue with how the P85D's 691 advertised HP is being marketed. I DONT CARE if it puts out slightly less peak HP then advertised, no big deal as the 0-60 times and a 5,000lb car speaks volumes - but this CAR DOES NOT OUTPUT 691HP AT ALL TIMES, ONLY WHILE UNDER 30MPH AND ONLY WHEN FULLY CHARGED. Hence, the reason I recommend Tesla puts an asterisk next to the advertised power because that power is ONLY ON TAP FOR SHORT LOW SPEED BURSTS.

 

[Matias]

. The S85 is advertised at 380HP, and the S60 is also advertised at 380HP..

And S60's 0-60 acceleration is 5.9 and S85 5.4, allthough S60 is lighter. We know, that the reason is S60's smaller battery.

 

[dogphlap]

Hi,
One cause of the reduced performance that goes with a non-fully charged battery would be the reduced terminal voltage of the battery pack. Power after all is the product of current and voltage and reduced voltage also means reduced current thus a double hit on the power from your traction motors.
There are several ways around this problem (other than the obvious one of keeping the SOC high for impressing kids and others with the wicked acceleration). You could trade the P85D in for a Dodge which won't wilt in the same way as your Tesla, it makes impressive noise and it is much cheaper. Sadly all other alternative vehicles are much dearer e.g. the Rimac at $1.8M, a fast but expensive Farrari or a 2.8s 0-60mph Porsche for half a million dollars. All those alternate vehicles could make it around a track for a full lap without going into thermal protection power reduction too. For the rest of us with less demanding motoring needs the Tesla is fine.

 

[Matias]

Hi,
One cause of the reduced performance that goes with a non-fully charged battery would be the reduced terminal voltage of the battery pack. Power after all is the product of current and voltage and reduced voltage also means reduced current thus a double hit on the power from your traction motors.
There are several ways around this problem (other than the obvious one of keeping the SOC high for impressing kids and others with the wicked acceleration). You could trade the P85D in for a Dodge which won't wilt in the same way as your Tesla, it makes impressive noise and it is much cheaper. Sadly all other alternative vehicles are much dearer e.g. the Rimac at $1.8M, a fast but expensive Farrari or a 2.8s 0-60mph Porsche for half a million dollars. All those alternate vehicles could make it around a track for a full lap without going into thermal protection power reduction too. For the rest of us with less demanding motoring needs the Tesla is fine.

What about Tesla putting the asterix or footnote explaining this to their website? That is out of the question? I think, it would be the cheapest and easiest solution.

 

[WarpedOne]

And S60's 0-60 acceleration is 5.9 and S85 5.4, allthough S60 is lighter. We know, that the reason is S60's smaller battery.

More correct wording would be "less powerful" battery.
What Tesla needs to do is publish power/torque chart for each Battery/Inverter/Motor combination.
It can be with full battery and every component at optimal temperature. It can be best case and measured on motor shaft(s combined) i.e. without that 1% gear loss.
They did it for the roadster and it is quite standard way of explaining what some drive-train is capable of.

 

[krisg81]

Hi,
One cause of the reduced performance that goes with a non-fully charged battery would be the reduced terminal voltage of the battery pack. Power after all is the product of current and voltage and reduced voltage also means reduced current thus a double hit on the power from your traction motors.
There are several ways around this problem (other than the obvious one of keeping the SOC high for impressing kids and others with the wicked acceleration). You could trade the P85D in for a Dodge which won't wilt in the same way as your Tesla, it makes impressive noise and it is much cheaper. Sadly all other alternative vehicles are much dearer e.g. the Rimac at $1.8M, a fast but expensive Farrari or a 2.8s 0-60mph Porsche for half a million dollars. All those alternate vehicles could make it around a track for a full lap without going into thermal protection power reduction too. For the rest of us with less demanding motoring needs the Tesla is fine.

Right on. Let's not pull out the "if you don't like it trade it for a Dodge" and also the "XXX car costs XXX more money with a similar 0-60, so end of discussing" card please. Thanks for your input though.

 

[sorka]

Although I'm impressed with the mathematicians in here and I like some of the info you guys are coming up with, let's consider the following.

1) Tesla advertises the P85D as 691HP. The S85 is advertised at 380HP, and the S60 is also advertised at 380HP.

2) There is little to no difference after 50MPH in acceleration across the P85D/S80/S60 fleet. Therefore advertised 691HP on the premium performance model is non-existent vs other models in the fleet. MORAL OF STORY: ADVERTISED 691 HORSEPOWER OF P85D IS ONLY TEMPORAILY AVAILABLE AT LOWER SPEEDS. In an ICE car, advertised HP is available AT ALL SPEEDS, but dependent on RPM - but you have all HP on tap at any speed (dependent on correct gear)

3) When fuel tank is low (battery) on P85D, performance suffers versus full tank (full charge). ICE vehicles don't care about the current level of fuel in the tank.

4) Since EV's peak horsepower seems to only work in a burst mode/temporary spike at low RPMs, why is Tesla able to advertise 691HP in the way a standard auto manufacturer rates an ICE vehicle? If a Corvette only outputted it's maximum advertised HP from 0-30MPH, and after that the same as a Camaro V6 with half the advertised power, the shat would hit the fan! There is a huge issue with how the P85D's 691 advertised HP is being marketed. I DONT CARE if it puts out slightly less peak HP then advertised, no big deal as the 0-60 times and a 5,000lb car speaks volumes - but this CAR DOES NOT OUTPUT 691HP AT ALL TIMES, ONLY WHILE UNDER 30MPH AND ONLY WHEN FULLY CHARGED. Hence, the reason I recommend Tesla puts an asterisk next to the advertised power because that power is ONLY ON TAP FOR SHORT LOW SPEED BURSTS.

If that were true, this P85D wouldn't walk this P85 from 35 all the way past 100 the entire time:

Tesla Model S P85D (691HP) vs P85 (415HP) 35 MPH Roll Race - YouTube

Also, I drove an S85 back to back with a P85D both with about an 85% SOC. There was so much difference between the two from 60 to the speed limited 80, it was like the S85 was my Prius by comparison.

This video, among others is typical of what the KW output shows WOT. Notice how peak isn't even reached until after 30 and it never lets up even up to 73 when the driver finally lets off.

Tesla Model S P85D 0-73 Dashboard View - YouTube

 

[lphe]

Perhaps I'm just taking your wording backwards? Calculating the movement of the car, and the power required... the motor actually has to produce more power than that, to both overcome the drag and to move the car... yes? no?

Yes, the motor must produce more power than what is shown on the plot to overcome aerodynamic drag, internal friction, and rolling resistance. If I use the range calculator at Tesla's website, the range of the P85D at 60 mph is 313 miles. The battery will output about 75 kWh of energy. Thus the power required for friction at 60 mph is:

75 kWh / 313 miles * 60 miles/hour = 14.4 kW.

 

[loco]

This video, among others is typical of what the KW output shows WOT. Notice how peak isn't even reached until after 30 and it never lets up even up to 73 when the driver finally lets off.

Yes, power starts decreasing at 90-100 mph, falling towards 240kW as speed increases.

 

[lphe]

Although I'm impressed with the mathematicians in here and I like some of the info you guys are coming up with, let's consider the following.

1) Tesla advertises the P85D as 691HP. The S85 is advertised at 380HP, and the S60 is also advertised at 380HP.

2) There is little to no difference after 50MPH in acceleration across the P85D/S80/S60 fleet. Therefore advertised 691HP on the premium performance model is non-existent vs other models in the fleet. MORAL OF STORY: ADVERTISED 691 HORSEPOWER OF P85D IS ONLY TEMPORAILY AVAILABLE AT LOWER SPEEDS. In an ICE car, advertised HP is available AT ALL SPEEDS, but dependent on RPM - but you have all HP on tap at any speed (dependent on correct gear)

3) When fuel tank is low (battery) on P85D, performance suffers versus full tank (full charge). ICE vehicles don't care about the current level of fuel in the tank.

4) Since EV's peak horsepower seems to only work in a burst mode/temporary spike at low RPMs, why is Tesla able to advertise 691HP in the way a standard auto manufacturer rates an ICE vehicle? If a Corvette only outputted it's maximum advertised HP from 0-30MPH, and after that the same as a Camaro V6 with half the advertised power, the shat would hit the fan! There is a huge issue with how the P85D's 691 advertised HP is being marketed. I DONT CARE if it puts out slightly less peak HP then advertised, no big deal as the 0-60 times and a 5,000lb car speaks volumes - but this CAR DOES NOT OUTPUT 691HP AT ALL TIMES, ONLY WHILE UNDER 30MPH AND ONLY WHEN FULLY CHARGED. Hence, the reason I recommend Tesla puts an asterisk next to the advertised power because that power is ONLY ON TAP FOR SHORT LOW SPEED BURSTS.

It is not possible for the car to produce 691 HP of power at lower speeds. The power that is output by the motor is:

P = 2*pi*torque*rpm/60

At lower speeds, power is limited by maximum torque of the motor. At 0 mph, the power output by the motor is 0. The reason the P85D accelerates faster at low speeds is that it has greater torque than then S85. The car needs to be going at a reasonable speed before it could possibly produce 691 HP of power. You can see in all the plots so far, power increases gradually from 0 kW at 0 mph up to some maximum at some speed and then levels off.

RPMs of the motor is proportional to the speed of the car. It is something like RPMs = 140*mph. I am not sure of the exact constant of proportionality.

- - - Updated - - -

If that were true, this P85D wouldn't walk this P85 from 35 all the way past 100 the entire time:

Tesla Model S P85D (691HP) vs P85 (415HP) 35 MPH Roll Race - YouTube

Also, I drove an S85 back to back with a P85D both with about an 85% SOC. There was so much difference between the two from 60 to the speed limited 80, it was like the S85 was my Prius by comparison.

This video, among others is typical of what the KW output shows WOT. Notice how peak isn't even reached until after 30 and it never lets up even up to 73 when the driver finally lets off.

Tesla Model S P85D 0-73 Dashboard View - YouTube

It looks like electrical power peaks at about 440 kW in the video. My best estimate for the maximum mechanical power output of the motor from post 256 is 385 kW. Thus efficiency is 385 / 440 = 87% which seems reasonable.

 

[loco]

It looks like electrical power peaks at about 440 kW in the video. My best estimate for the maximum mechanical power output of the motor from post 256 is 385 kW. Thus efficiency is 385 / 440 = 87% which seems reasonable.

As it was pointed out, scale is logarithmic. 4 marks between 240 and 480 are 275, 316, 363, 417kW.
I see only the third mark in my car. P85D 0-200 cold - YouTube

 

[lphe]

As it was pointed out, scale is logarithmic. 4 marks between 240 and 480 are 275, 316, 363, 417kW.
I see only the third mark in my car. P85D 0-200 cold - YouTube

Yes. It looks like the maximum power occurs at about 85% of the distance between 240 and 480. So power is 240*2^(.85) = 433. I was being generous.

 

[bp1000]

1) Tesla advertises the P85D as 691HP. The S85 is advertised at 380HP, and the S60 is also advertised at 380HP.

2) There is little to no difference after 50MPH in acceleration across the P85D/S80/S60 fleet. Therefore advertised 691HP on the premium performance model is non-existent vs other models in the fleet. MORAL OF STORY: ADVERTISED 691 HORSEPOWER OF P85D IS ONLY TEMPORAILY AVAILABLE AT LOWER SPEEDS. In an ICE car, advertised HP is available AT ALL SPEEDS, but dependent on RPM - but you have all HP on tap at any speed (dependent on correct gear)

Don't agree, there are videos of rolling acceleration tests P85D vs P85. In the video the P85 got the jump, by the time they got to about 50mph the p85d pulls a huge gap.

The lack of gears does become an issue above 100 at a finger in the air guess.

With the release of v6.2 with a 155mph speed limit on the p85d they may have re-mapped some of the power curve to enable the higher top speed, this may make it a bit quicker at higher speed who knows.

My simple observation is its extremely fast between 0 and 100mph. It does tail off after about 70-80mph but as a road car does this matter, its incredibly quick between legal speeds. (Maybe not so much for our german cousins).

There is video evidence showing devastating "in gear" performance.